1. Field of the Invention
This invention relates generally to optical devices, and more particularly to an improved optical grating device and system employing electrical means to control the direction or spatial patterns of optical beams.
2. Brief Description of the Prior Art
Devices for controlling the direction of an optical beam or the spatial patterns of illumination produced by a laser have been very limited in the past, and confined almost entirely to mechanical methods, such as galvanic mirrors. An alternative method and apparatus whereby this spatial control could be performed electronically with no moving parts would allow much faster and more reliable control of optical beams.
Spatial light modulators, devices in which optical properties of the material are spatially controlled, have previously been very large compared to the wavelength of light, and have therefore been useless for obtaining diffraction patterns. Present semiconductor technology, however, allows the use of quantum well devices to make much smaller spatial light modulators where diffraction effects dominate. Since these devices are intrinsically very fast, and can be made lithographically, they are useful in rapidly controlling far-field patterns of illumination and obtaining beam steering through diffraction. These devices can work in transmission mode, where the light passes directly through the quantum well region, or in reflection mode, where external or integrated mirrors are used to enhance reflectivity changes and contrast.